31 October 1997 Nematic Fabry-Perot etalons for ground- and space-based atmospheric remote sensing
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Abstract
Birefringent, nematic liquid crystals (LC) have been laminated between the substrates of several Fabry-Perot etalons. The application of an electric field allows the effective index of refraction of the LC to be varied. A polymer alignment layer is used to align the crystals perpendicular to the optical axis of the Fabry-Perot etalon. An oscillating electric field is used to rotate the crystal around the optical axis of the etalon, effectively changing the index of refraction. This change in index is used to tune the Fabry-Perot etalon in a manner similar to traditional pressure and mechanical tuning systems. However, the approach described here has the advantage of producing a solid-state etalon that is tunable without needing a bulky pressure system or environmentally sensitive piezo-electric stacks. A two etalon spectrometer consisting of two Fabry- Perot etalons coupled to a CID detector has been developed. A suppression etalon with a gap of 10 micrometers , and a LC wit a refractive index of 1.63 are used in conjunction with a high resolution etalon to produce an instrument ideal for observing the atomic spectra of hot, light neutral species and the molecular bands in the atmosphere. Several other etalons have been constructed to further develop this technology. Clear apertures greater than 2 inches have been achieved, and a hybrid spacer technique has been developed to allow for etalons with spacings of up to 1 cm. Fabry- Perot partial reflective coatings capable of operation from the visible to the NIR will also be discussed.
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John Noto, Kristin E. Schneller, William J. Schneller, Robert B. Kerr, R. A. Doe, "Nematic Fabry-Perot etalons for ground- and space-based atmospheric remote sensing", Proc. SPIE 3118, Imaging Spectrometry III, (31 October 1997); doi: 10.1117/12.278939; https://doi.org/10.1117/12.278939
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